I've found a different thread about a similar topic but the poster answered his own question...

When you have two (identical) secondaries, you can wind them in series for double the voltage, or in parallel for double the current handling (true, right?).

==> What if you have idedntical secondaries but they are wound on different cores? Do the same rules apply? I would think you can still put them in series and the voltages would still add, but I'm not sure anymore about putting them in parallel.

It depends on how the primaries are connected. For series primaries the secondaries may be connected in paralell even when they are not exactly identical, however, for paralell primaries you have to check whether both transformers have exactly the same turn ratios, because there will be parasitistic currents flowing from one transformer to the other otherwise.

Hi,
for parallel primaries I agree with Eva. Take care with paralleling transformers.
Series primaries ????
Series secondaries is OK for transformers that are nominally the same.
But keep in mind the voltage stress if you are using high voltage transformers. Peak voltage to ground and peak voltage to primary must both be below the maximum the transformer can take as a working voltage.

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regards Andrew T.
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